<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  <div id="root">
    <p>{{ name }}</p>
  </div>
  <script src="../node_modules/vue/dist/vue.js"></script>
  <script>
  
    let app = new Vue( {
      el: '#root',
      data: {
        name: 'jim',
        a: {
          b: {
            c: 'jim'
          }
        }
      },
      watch: {
        // 
        'a.b.c': function ( o, n ) {
          console.log( '>>>>', o, n );
        } 
      }
    } ) ;


  </script>
</body>
</html>